a blocker of Apamin-sensitive Ca²⁺-activated K⁺ channels.

31-amino acid peptide with 3 disulfide bridges. Synthetic‚ originally from Leiurus quinquestriatus hebraeus scorpion venom.

Scyllatoxin (Leiurotoxin I) completely inhibits Apamin binding to rat brain synaptosomal membranes (Ki = 75 pM) (1) (2).
Like Apamin‚ Scyllatoxin blocks the epinephrine-induced relaxation of guinea pig teniae coli (ED₅₀ = 6.5 nM) (1).
A series of analogs that allow the use of different labeling techniques have also been prepared: the [Tyr²] Scyllatoxin analog‚ allowing labelling by iodination‚ is available.

1. Chicci et al., "Purification and characterization of a unique, potent inhibitor of apamin binding from Leiurus quinquestriatus hebraeus venom." J. Biol. Chem.,(1988). 263(21):10192-10197
2. Auguste et al., "Leiurotoxin I (Scyllatoxin), a peptide ligand for Ca2+-activated K+ channels." J. Biol. Chem., (1990) 265(8):4753-4759
3. Martins et al., FEBS Letters,(1990) 260(2):249-253